Method and apparatus for scheduling communication for low capability devices

ABSTRACT

Methods and apparatus are described for a User Equipment (UE) with reduced processing capabilities (e.g., Machine Type Communication (MTC) UE) to transmit and receive signaling are provided. The Downlink Control Information (DCI) formats scheduling a transmission of a Physical Uplink Shared CHannel (PUSCH) or a reception of a Physical Downlink Shared CHannel (PDSCH) are designed and have a smaller size than respective DCI formats for conventional UEs. DCI formats scheduling PUSCHs to or PDSCHs for a group of MTC UEs are also designed and can have a same size as DCI formats scheduling PUSCH or PDSCH for an individual MTC UE.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation application of prior Application No.17/497,415 filed on Oct. 8, 2021, which will be issued as U.S. Pat. No.11,659,570 on May 23, 2023; which is a continuation application of priorApplication No. 16/872,739 filed on May 12, 2020, which has issued asU.S. Pat. No. 11,172,480 on Nov. 9, 2021; which is a continuationapplication of prior Application No. 16/050,360 filed on Jul. 31, 2018,which has issued as U.S. Pat. No. 10,652,875 on May 12, 2020; which is acontinuation application of prior Application No. 13/750,214 filed onJan. 25, 2013, which has issued as U.S. Pat. No. 10,039,088 on Jul. 31,2018; and which is based on and claims priority under 35 U.S.C. §119(e)of a U.S. Provisional Application No. 61/590,991 filed on Jan. 26, 2012,the disclosure of each of which is incorporated by reference herein inits entirety.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to wireless communication systems. Moreparticularly, the present invention relates to the design of downlinkcontrol information formats scheduling data transmissions to or datareceptions from User Equipment (UE) with limited capabilities.

2. Description of the Art

A communication system includes a DownLink (DL) that conveystransmission signals from transmission points such as Base Stations (BSor NodeBs) to User Equipments (UEs), and an UpLink (UL) that conveystransmission signals from UEs to reception points such as NodeBs. A UE,also commonly referred to as a terminal or a mobile station, may befixed or mobile and may be a cellular phone, a personal computer device,and the like. A NodeB, which is generally a fixed station, may also bereferred to as an access point or other equivalent terminology.

DL signals includes data signals, which carry the information content,control signals, and Reference Signals (RSs), which are also known aspilot signals. A NodeB conveys data information to UEs throughrespective Physical Downlink Shared CHannels (PDSCHs) and controlinformation through respective DL Control CHannels (CCHs). Multiple RStypes may be supported, such as for example a Common RS (CRS)transmitted over substantially the entire DL BandWidth (BW) BW and theDeModulation RS (DMRS) transmitted in a same BW as an associated PDSCH.

UL signals also include data signals, control signals and RSs. UEsconvey data information to NodeBs through respective Physical UplinkShared CHannels (PUSCHs) and control information through respectivePhysical Uplink Control CHannels (PUCCHs). A UE transmitting datainformation may also convey control information through a PUSCH. The RSmay be a DMRS or a Sounding RS (SRS) which a UE may transmitindependently of a PUSCH.

FIG. 1 is a diagram illustrating a structure for a DownLink (DL)Transmission Time Interval (TTI) according to the related art.

Referring to FIG. 1 , a DL TTI includes one subframe 110 which includestwo slots 120 and a total of

N_(symb)^(DL)

symbols used for transmitting data information, DL Control Information(DCI), or RS. The first

M_(symb)^(DL)

symbols are used to transmit DL CCHs 130. The first

M_(symb)^(DL)

symbols may be dynamically indicated in each DL TTI through a PhysicalControl Format Indicator CHannel (PCFICH). The remaining

N_(symb)^(DL) − M_(symb)^(DL)

symbols are primarily used to transmit PDSCHs 140. The transmission BWincludes frequency resource units referred to as Resource Blocks (RBs).Each RB includes

N_(sc)^(RB)

sub-carriers, or Resource Elements (REs), and a UE can be allocatedM_(PDSCH) RBs for a total of

M_(sc)^(PDSCH) = M_(PDSCH) ⋅ N_(sc)^(RB)

REs for a PDSCH transmission BW in a DL TTI. Some REs in some symbolscontain CRS (or DMRS) 150 which enable channel estimation and coherentdemodulation of data signals or control signals at a UE. A PDSCHtransmission in a second slot may be at a same BW or at a different BWthan in a first slot. In the former case, the PDSCH transmission isreferred to as localized. In contrast, in the latter case the PDSCHtransmission is referred to as distributed.

A PDSCH transmission to a UE or a PUSCH transmission from a UE may bescheduled by a NodeB through a transmission of a respective Physical DLControl CHannel (PDCCH) conveying a DCI format which providesinformation for a respective PDSCH or PUSCH transmission as it issubsequently described. A PDSCH or a PUSCH transmission may also beSemi-Persistently Scheduled (SPS) by a NodeB through higher layersignaling, such as Radio Resource Control (RRC) signaling, in which caseit occurs at predetermined TTIs and with predetermined parametersspecified by the higher layer signaling.

To avoid a PDCCH transmission to a UE that is blocking a PDCCHtransmission to another UE, a location of each PDCCH transmission in thetime-frequency domain of a DL control region is not unique. Therefore, aUE may perform multiple decoding operations per DL subframe to determinewhether there are PDCCHs intended for the UE in a DL subframe. Theresource unit for a PDCCH transmission is referred to as a ControlChannel Element (CCE) and includes multiple REs. For a given number ofDCI format bits, a number of CCEs for a respective PDCCH depends on achannel coding rate (Quadrature Phase Shift Keying (QPSK) is assumed asthe modulation scheme). A NodeB may use a lower channel coding rate(e.g., more CCEs) for transmitting a PDCCH to a UE experiencing low DLSignal to Interference and Noise Ratio (SINR) than to a UE experiencinga high DL SINR. The CCE Aggregation Levels (ALs) may include, forexample, 1, 2, 4, and 8 CCEs.

A NodeB may also transmit ACKnowledgement information associated with aHybrid Automatic Repeat reQuest (HARQ) process (HARQ-ACK information)for transmission of data Transport Blocks (TBs) in respective PUSCHs.HARQ-ACK signals through respective Physical Hybrid-ARQ IndicatorCHannels (PHICHs) inform respective UEs whether transmissions ofrespective data TBs were correctly or incorrectly detected by a NodeB.For a PUSCH transmission scheduled by PDCCH, the PHICH resourcen_(PHICH) can be assumed to be derived as in Equation (1)

$\begin{matrix}{n_{\text{PHICH}} = f\left( {I_{\text{PRB\_RA}}^{\text{lowet\_index}},\text{n}_{\text{DMRS}},N_{\text{PHICH}}} \right)} & \text{­­­(1)}\end{matrix}$

where ƒ (·) is a function of a first UL RB

I_(PRB_RA)^(lowet_index)

for a respective PUSCH, of a n_(DMRS) parameter provided in a DCI formatscheduling the PUSCH as it is subsequently described, and of otherparameters. N_(PHICH) is informed to a UE through higher layer signalingby a NodeB. For a SPS PUSCH, a PHICH resource can be assigned to a UEthrough higher layer signaling.

The DL control region in FIG. 1 uses a maximum of

M_(symb)^(DL) = 3

subframe symbols, and a PDCCH is transmitted substantially over a totalDL BW. As a consequence, such control region has limited capacity andcannot achieve interference coordination in the frequency domain.Expanded PDCCH capacity or PDCCH interference coordination in thefrequency domain is needed in several cases. One such case is anextensive use of spatial multiplexing for PDSCH transmissions in whichmultiple DL SAs schedule same PDSCH resources to respectively multipleUEs. Another case is for heterogeneous networks in which DLtransmissions in a first cell experience strong interference from DLtransmissions in a second cell and DL interference co-ordination in thefrequency domain between the two cells is needed.

A direct extension of a DL control region as in FIG. 1 to more than

M_(symb)^(DL) = 3

subframe symbols is not possible at least due to a requirement tosupport UEs which cannot be aware of such extension. An alternative isto support DL control signaling in a PDSCH region according to therelated art by using individual RBs to transmit control signals. A PDCCHtransmitted in RBs of a PDSCH region according to the related art willbe referred to as Enhanced PDCCH (EPDCCH).

FIG. 2 is a diagram illustrating EPDCCH transmissions in a DL subframeaccording to the related art.

Referring to FIG. 2 , although EPDCCH transmissions start immediatelyafter a DL control region 210 according to the related art and are overall remaining subframe symbols, EPDCCH transmissions may instead alwaysstart at a fixed location, such as the fourth subframe symbol, andextend over a part or all of the remaining subframe symbols. EPDCCHtransmissions occur in four RBs, 220, 230, 240, and 250, while remainingRBs can be used to transmit PDSCHs 260, 262, 264, 266, and 268. Anenhanced PCFICH (EPCFICH) or an Enhanced PHICH (EPHICH) may also besupported. In a DL TTI, an Enhanced Control CHannel (ECCH), referring toan EPDCCH, an EPCFICH, or an EPHICH, may be transmitted in a same RB, inwhich case the ECCH is referred to as localized, or over multiple RBs,in which case the ECCH is referred to as distributed.

Demodulation of information conveyed by an EPDCCH may be based on a CRSor on a DMRS. A DMRS is transmitted in some subframe symbols and in asubset of REs in RBs used for an associated EPDCCH transmission.

FIG. 3 is a diagram illustrating a DMRS structure in a RB over a DL TTIaccording to the related art.

Referring to FIG. 3 , the DMRS REs 310 are placed in some subframesymbols of a RB used to transmit an ECCH. For orthogonal multiplexing ofdifferent DMRS, a first DMRS transmission is assumed to use anOrthogonal Cover Code (OCC) of {1, 1} over two respective REs that arelocated in a same frequency position and are successive in the timedomain while a second DMRS transmission is assumed to use an OCC of {1,-1 } .

FIG. 4 is a diagram illustrating an encoding and transmission processfor a DCI format according to the related art.

Referring to FIG. 4 , a NodeB separately encodes and transmits each DCIformat in a respective PDCCH or EPDCCH. A Radio Network TemporaryIdentifier (RNTI) for a UE, for which a DCI format is intended for,masks a Cyclic Redundancy Check (CRC) of a DCI format codeword in orderto enable the UE to identify that a particular DCI format is intendedfor the UE. The CRC of (non-coded) DCI format bits 410 is computed usinga CRC computation operation 420, and the CRC is then masked using anexclusive OR (XOR) operation 430 between CRC and RNTI bits 440. The XORoperation 430 is defined as: XOR(0,0) = 0, XOR(0,1) = 1, XOR(1,0) = 1,XOR(1,1) = 0. The masked CRC bits are appended to DCI format informationbits using a CRC append operation 450, channel coding is performed usinga channel coding operation 460, for example using a Tail BitingConvolutional Code (TBCC), followed by rate matching operation 470applied to allocated resources, and finally, an interleaving and amodulation 480 operation, after which the output control signal 490 istransmitted. In the present example, both a CRC and a RNTI include 16bits.

FIG. 5 is a diagram illustrating a reception and decoding process for aDCI format according to the related art.

Referring to FIG. 5 , a UE receiver performs the reverse operations of aNodeB transmitter to determine whether the UE has a DCI formatassignment in a DL subframe. A received control signal 510 isdemodulated and the resulting bits are de-interleaved at operation 520,a rate matching applied at a NodeB transmitter is restored throughoperation 530, and control data is subsequently decoded at operation540. After decoding the control data, DCI format information bits 560are obtained after extracting CRC bits 550 which are then de-masked 570by applying the XOR operation with a UE RNTI 580. Finally, a UE performsa CRC test 590. If the CRC test passes, a UE detects a DCI format anddetermines parameters for signal reception or signal transmission. Ifthe CRC test does not pass, a UE disregards a presumed DCI format.

FIG. 6 is a diagram illustrating a PUSCH transmission structure over anUL TTI according to the related art.

Referring to FIG. 6 , an UL TTI includes one subframe 610 which includestwo slots. Each slot 620 includes

N_(symb)^(UL)

symbols 630 used for transmitting data information, UL ControlInformation (UCI), or RS. A PUSCH transmission in one slot may be eitherat a same BW or at a different BW than a PUSCH transmission in the otherslot. Some symbols in each slot are used to transmit RS 640 whichenables channel estimation and coherent demodulation of received datainformation and/or UCI at a NodeB. A UE is allocated M_(PUSCH) RBs 650for a total of

M_(sc)^(PUSCH) = M_(PUSCH) ⋅ N_(sc)^(RB)

REs for a PUSCH transmission BW. The last subframe symbol may be usedfor SRS transmission 660 from one or more UEs. The main purpose of aSounding Reference Signal (SRS) is to provide a NodeB with an estimatefor a UL channel medium experienced by a respective UE. SRS transmissionparameters for each UE are configured by a NodeB through higher layersignaling.

A UE transmits UCI to provide a NodeB information related to PDSCHtransmissions to the UE or PUSCH transmissions from the UE. UCI includesHARQ-ACK information regarding a correct or incorrect detection of dataTBs, Channel State Information (CSI) for a DL channel a UE experiences,and a Service Request (SR) informing a NodeB that a UE has data totransmit. A UE transmitting PUSCH may also provide a NodeB with a BufferStatus Report (BSR) informing a NodeB of an amount of data a UE has fortransmission in its buffer.

FIG. 7 is a diagram illustrating a PUCCH structure for HARQ-ACK signaltransmission according to the related art.

Referring to FIG. 7 , HARQ-ACK signals and RS enabling coherentdemodulation of HARQ-ACK signals are transmitted in one slot 710 of aPUCCH subframe including 2 slots. The transmission in the other slot canbe at a different part of an UL BW. HARQ-ACK information bits 720modulate 730 a Zadoff-Chu (ZC) sequence 740, for example using BinaryPhase Shift Keying (BPSK) for 1 HARQ-ACK bit or QPSK for 2 HARQ-ACKbits, which is then transmitted after performing a Inverse Fast FourierTransform (IFFT) operation 750. Each RS 760 is transmitted using anunmodulated ZC sequence.

For an UL system BW of

N_(RB)^(UL)

RBs, a ZC sequence

r_(u, v)^((α))(n)

is defined by a Cyclic Shift (CS) α of a base ZC sequence

${\overline{r}}_{u,v}(n)$

according to

$r_{u,v}^{(\alpha)}(n) = e^{j\alpha n}{\overline{r}}_{u,v}(n),\quad 0 \leq n < M_{\text{sc}}^{\text{RS}}\mspace{6mu},$

where

M_(sc)^(RS) = mN_(sc)^(RB)

is the length of the ZC sequence,

1 ≤ m ≤ N_(RB)^(UL),

and

${\overline{r}}_{u,v}(n) = x_{q}\left( {n\mspace{6mu}{mod}N_{\text{ZC}}^{\text{RS}}} \right)$

where the q^(th) root ZC sequence is defined by

$x_{q}(m) = \exp\left( \frac{- j\pi qm\left( {m + 1} \right)}{N_{\text{ZC}}^{\text{RS}}} \right)$

,

0 ≤ m ≤ N_(ZC)^(RS) − 1

with q given by

$q = \left\lfloor {\overline{q} + {1/2}} \right\rfloor + v \cdot \left( {- 1} \right)^{\lfloor{2\overline{q}}\rfloor}$

and q̅ given by

$\overline{q} = N_{\text{ZC}}^{\text{RS}} \cdot {\left( {u + 1} \right)/31}.$

The length

N_(ZC)^(RS)

of a ZC sequence is given by the largest prime number such that

N_(ZC)^(RS) < M_(sc)^(RS).

Multiple RS sequences can be defined from a single base sequence throughdifferent values of _(α). A PUCCH is assumed to be transmitted in one RB

(M_(sc)^(RS) = N_(sc)^(RB)).

FIG. 8 is a diagram illustrating a transmitter for a ZC sequenceaccording to the related art.

Referring to FIG. 8 , a mapper 820 maps a ZC sequence 810 to REs of anassigned transmission BW as REs of the assigned transmission BW areindicated by RE selection unit 825. An IFFT is then performed by IFFTunit 830, a CS is applied to the output by CS unit 840, followed byscrambling with a cell-specific sequence using scrambler 850. Aresulting signal is filtered by filter 860, a transmission power isapplied by power amplifier 870, and a ZC sequence is transmitted 880. Asan example, the reverse operations are performed at a NodeB receiver.Without modulation, a ZC sequence serves as a RS. With modulation, a ZCsequence serves as a HARQ-ACK signal or as a CSI signal. The SR may betransmitted using an unmodulated ZC sequence through On-Off Keying.

Different CSs of a ZC sequence provide orthogonal ZC sequences.Therefore, different CSs α of a same ZC sequence can be allocated todifferent UEs in a same PUCCH RB and achieve orthogonal multiplexing fortransmissions of HARQ-ACK signals or of CSI signals, and RS. For a RBincluding

N_(sc)^(RS) = 12

REs, there are 12 different CS. The number of usable CS depends on thechannel dispersion characteristics and can typically range between 3 and12. Orthogonal multiplexing can also be in the time domain using OCCwhere PUCCH symbols conveying a same signal type in each slot aremultiplied with elements of an OCC. For example, for the structure inFIG. 7 , an HARQ-ACK signal in each slot can be modulated by a length-4OCC, such as a Walsh-Hadamard (WH) OCC, while a RS in each slot can bemodulated by a length-3 OCC, such as a DFT OCC. In this manner, themultiplexing capacity per RB per subframe is increased by a factor of 3(e.g., determined by the OCC with the smaller length N_(oc)).

A UE may implicitly determine a PUCCH resource, n_(PUCCH), for HARQ-ACKsignal transmission, in response to a PDSCH reception scheduled by aPDCCH, based on a first CCE, n_(CCE), used to transmit the PDCCH as inEquation (2)

$\begin{matrix}{n_{\text{PUCCH}} = n_{\text{CCE}} + N_{\text{PUCCH}}} & \text{­­­(2)}\end{matrix}$

where N_(PUCCH) is an offset informed to the UE by the NodeB throughhigher layer signaling. The PUCCH resource provides a CS and an OCC atan RB for HARQ-ACK signal transmission. For SPS PDSCH, a PUCCH resourcefor HARQ-ACK signal transmission may be assigned to a UE by a NodeBthrough higher layer signaling.

Encoding of DCI is based on a TBCC while encoding of data information isbased on a turbo code. This is due to the better performance of a TBCCfor payloads less than about 100 bits, such as the TBCC included in DCIformats, and the better performance of a turbo code for payloads aboveabout 100 bits, such as the TBCC included in data TBs.

FIG. 9 is a diagram providing a detection performance for a TBCC and fora turbo code according to the related art.

Referring to FIG. 9 , the detection performance is provided in terms ofrequired SINR to achieve a target BLock Error Rate (BLER) of 0.01 whichis typically used for DCI, as a function of the payload assuming acoding rate of ⅓. In general, as a target BLER increases, a number ofbits for which a TBCC outperforms a turbo code decreases. For example,although not illustrated for brevity, for a target BLER of 0.1 which istypically used for detection of data information, a TBCC outperforms aturbo code for payloads smaller than about 70-80 bits.

A DCI format scheduling a PDSCH or a PUSCH includes several InformationElements (IEs). Different DCI formats may be associated with differentPDSCH or PUSCH Transmission Modes (TMs) configured to a UE. For example,a first DCI format can be used to schedule a transmission of only onedata TB to or from a UE while a second DCI format can be used toschedule a transmission of up to two data TBs. Exemplary embodiments ofthe present invention focus on DCI formats associated with one data TBand on a DCI format scheduling PDSCH having a same size as a DCI formatscheduling PUSCH.

Table 1 provides IEs for a DCI format scheduling a PUSCH for a maximumof one data TB.

TABLE 1 IEs of a DCI Format Scheduling PUSCH (DCI Format 0) IE Number ofBits Differentiation Flag for 0/1A 1 RA⌈log₂(N_(RB)^(UL)(N_(RB)^(UL) + 1)/2)⌉ FH Flag 1 MCS and RV 5 NDI 1 TPCCommand for PUSCH 2 CS and OCC Index ^(n) _(DMRS) 3 CSI Request 1 SRSRequest 1 DAI (TDD) 0 (FDD) or 2 (TDD) UL Index (TDD) 0 (FDD) or 2 (TDD)Padding Bits for 0=1A 1 RNTI 16 Total 43 (FDD) or 47 (TDD)

A differentiation flag IE indicates one of two DCI formats, DCI format 0and DCI format 1A, having a same size. For example, a value of zeroindicates DCI format 0 and a value of one indicates DCI format 1A.

A Resource Allocation (RA) IE indicates a part of an UL BW for a PUSCHtransmission. A UE is allocated a number of consecutive RBs and for anUL BW including

N_(RB)^(UL)

, the possible RB allocations can be represented by

⌈log₂(N_(RB)^(UL)(N_(RB)^(UL) + 1)/2)⌉

bits where

⌈⋅⌉

is the ceiling function which rounds a number to the next greaterinteger.

A Frequency Hopping (FH) flag IE indicates whether the PUSCHtransmission is in a same BW or in a different BW in a second slotrelative to a first slot.

A Modulation and Coding Scheme (MCS) and a Redundancy Version (RV) IEprovides, through one of a first number of states, a modulation scheme(QPSK, QAM16, QAM64) and a code rate of a turbo code for a transmissionof a data TB. In a case of a data TB retransmission according to aphysical layer HARQ process, this RV IE provides through one of theremaining number of states the RV for an Incremental Redundancy (IR)assumed to be apply using turbo encoding assuming non-adaptive HARQretransmissions (e.g., same MCS as the initial transmission for a samedata TB).

A New Data Indicator (NDI) IE informs a UE as to whether a data TB theUE should transmit is a new one or whether the data TB corresponds to aretransmission of a previous data TB (e.g., a synchronous HARQ processis assumed for PUSCH transmissions).

A CS and OCC index IE, _(DMRS), informs a UE of a CS and OCC the UEshould apply to a DMRS transmission.

A CSI request IE informs a UE whether the UE should include CSI feedbackin a PUSCH transmission.

A SRS request IE informs the UE whether the UE should transmit an SRSaccording to a configured set of SRS transmission parameters (e.g., theother state indicates no SRS transmission). The SRS transmissionparameters include the SRS transmission BW, the CS of the respective ZCsequence, the starting BW position of the transmission, and so on.

For a TDD system, two more IEs are included in DCI formats schedulingPUSCH transmissions. A first IE is a Downlink Assignment Index (DAI) IEinforming a UE of a number of PDSCH transmissions to the UE within abundling window which is defined as a number of DL subframes for which aUE provides HARQ-ACK feedback to a NodeB in a same UL subframe. Based onthe DAI value, a UE determines a number of HARQ-ACK bits, if any, the UEincludes in a PUSCH transmission. A second IE is an UL index IE whichinforms a UE of an UL subframe for a PUSCH transmission. This isapplicable to TDD configurations of UL-DL subframes having more ULsubframes than DL subframes. The partitioning of UL-DL subframes isperiodic per frame and a frame may include, for example, 10 subframes.

Finally, padding bits may be included in DCI format 0, if applicable, inorder to make its size equal to that of DCI format 1A.

Table 2 provides IEs for a DCI format scheduling a PDSCH for a maximumof one data TB.

TABLE 2 IEs of a DCI Format Scheduling PUSCH (DCI Format) IE Number ofBits Differentiation Flag for 0/1A 1 RA⌈log₂(N_(RB)^(DL)(N_(RB)^(DL) + 1)/2)⌉ Distributed/LocalizedTransmission (FH) Flag 1 MCS 5 NDI 1 RV 2 HARQ Process Number 3 (FDD) or4 (TDD) TPC Command for PUCCH 2 SRS Request 1 DAI (TDD) 0 (FDD) or 2(TDD) Padding Bits for 0=1A 0 RNTI 16 Total (FDD) 43

The functionality and size of a differentiation flag IE, a RA flag IE, adistributed/localized flag IE, an MCS IE, a NDI IE, and a SRS IE aresame as for DCI format 0, and this also holds for the padding bits.Asynchronous HARQ is assumed for PDSCH transmissions and a RV isprovided by a separate IE while an MCS IE provides only MCS information.

A HARQ process number IE is included in DCI formats scheduling PDSCHtransmissions to support an asynchronous HARQ process.

A Transmit Power Control (TPC) command IE provides a TPC command for aUE to adjust a power of an HARQ-ACK signal transmitted in a PUCCH inresponse to a PDSCH reception by a UE.

A DAI IE provides a counter for a number of PDSCH transmissions to a UEin a bundling window. Using a DAI IE, a UE can identify missed PDSCHreceptions, due to respective missed PDCCH detections within a bundlingwindow, unless a UE does not detect a PDCCH in any subsequent subframeafter one or more subframes of missed PDCCHs.

UEs may be able to communicate over an entire system BW and with largedata TB Sizes (TBS) or over only a part of a system BW and with limiteddata TBS. In the former case, UEs can benefit from most or allcapabilities of a network for PDSCH receptions or PUSCH transmissions,are typically used by humans, and will be referred to as conventionalUEs. In the latter case, UEs have substantially reduced capabilitiescompared to UEs according to related art in order to substantiallyreduce their cost, are typically associated with machines, and will bereferred to as Machine Type Communication (MTC) UEs.

MTC UEs are low cost devices targeting various low data rate trafficapplications including smart metering, intelligent transport systems,consumer electronics, and medical devices. Typical traffic patterns fromMTC UEs are characterized by low duty cycles and small data packets(e.g., small TBS) in the order of a few tens or a few hundred bytes. MTCUEs are typically low mobility but high mobility UEs, such as forexample motor vehicles, also exist. Also, unlike UEs according to therelated art, MTC UEs generate more UL traffic than DL traffic and amajority of DL traffic is higher layer control information forconfiguration.

Unlike UEs according to the related art, such as for example asmartphone, which may have many features, MTC UEs may have only aminimum of necessary features. Accordingly, the modem becomes theprimary contributor to the cost of an MTC UE. Therefore, main costdrivers for MTC UEs are the Radio Frequency (RF) components and theDigital Base-Band (DBB) components mainly for the receiver. The RFcomponents include a power amplifier, filters, a transceiver radiochains, and possibly a duplexer (for full duplex FDD operation). The DBBcomponents of a UE receiver include a channel estimator, a channelequalizer, a PDCCH decoder, a PDSCH decoder, and a subframe buffer. Forexample, a channel estimator may be based on a Minimum Mean Square Error(MMSE) estimator, a channel equalizer may be an FFT, a PDCCH decoder maybe a decoder for a TBCC, and a data decoder may be a decoder for a TurboCode (TC).

RF costs are related to implementation and production methods as well asto design choices. For example, considering economies of scale, it maybe more cost effective to use a same amplifier for conventional UEs andfor MTC UEs (e.g., this will also ensure the same UL coverage) while anumber of transmitter antennas for MTC UEs may be limited to one.

DBB costs are related to the communication capabilities of MTC UEs andare dominated by the receiver complexity which is typically about anorder of magnitude larger than the transmitter complexity. As channelestimator complexity, FFT complexity, and subframe bufferingrequirements are directly associated to a reception BW, DL transmissionsto MTC UEs may be over a smaller BW, at least in the DBB, than DLtransmissions to conventional UEs. For example, DL transmissions to MTCUEs may be over a 1.4 MHz BW at the DBB while DL transmissions toconventional UEs may be over a 20 MHz BW.

A complexity of a PDCCH decoder depends on a number of decodingoperations an MTC UE performs per subframe. As MTC UEs do not need tosupport a same number of TMs as conventional UEs, for example MTC UEsmay not need to support spatial multiplexing for PDSCH receptions orPUSCH transmissions, a maximum number of decoding operations an MTC UEneeds to perform per subframe can be significantly smaller than that fora conventional UE. A complexity of a PDSCH decoder depends on a maximumsupportable TBS. Allowing for a relatively small maximum TBS for MTC UEslimits an associated decoder complexity.

MTC UEs are assumed to access a communication system in a same manner asconventional UEs. Synchronization signals are first acquired toestablish synchronization with a NodeB followed by a detection of aBroadcast CHannel (BCH) that conveys essential information forsubsequent communication between a NodeB and UEs (e.g., conventional UEsor MTC UEs). Regardless of a DL BW of a communication system,synchronization signals and BCH are assumed to be transmitted over aminimum DL BW located in the center of a DL BW of a communicationsystem, such as for example in a middle six RBs of a DL BW, and over anumber of Orthogonal Frequency Division Multiplexing (OFDM) symbols in asubframe. After establishing communication with a NodeB, a differentpart of a DL BW may be allocated to an MTC UE.

One aspect of supporting communication for MTC UEs is a design of DCIformats scheduling PDSCH transmissions to or PUSCH transmissions fromMTC UEs. Respective TMs and a number of decoding operations for PDCCHscarrying respective DCI formats should be defined with an objective ofminimizing DBB complexity while providing desired functionalities. It isdesirable for MTC UEs to perform a smaller number of decoding operationsthan conventional UEs without impacting an associated schedulingefficiency and functionality.

Another aspect is a reduction in a PDCCH overhead associated withscheduling PDSCH transmissions to or PUSCH transmissions from MTC UEs.As TBS conveyed to or from MTC UEs can be significantly smaller than TBSconveyed to or from conventional UEs, similar reductions in a PDCCHoverhead are needed for efficient operation of a communication system.

Finally, as communication with MTC UEs is typically UL intensive and aDBB receiver complexity is significantly larger than a DBB transmittercomplexity, a more efficient coding method can be used for datatransmission from MTC UEs in a PUSCH than for data transmission to MTCUEs in a PDSCH.

Therefore, there is a need to design transmissions modes and respectiveDCI formats associated with PDSCH transmissions to or PUSCHtransmissions from MTC UEs.

There is another need to reduce a PDCCH overhead associated withscheduling PDSCH transmissions to or PUSCH transmissions from MTC UEs.

In addition, there is another need to define different coding methodsfor data transmitted to an MTC UE than for data transmitted from an MTCUE.

Therefore, a need exists for an apparatus, system, and method fordesigning transmissions modes and respective DL Control Information(DCI) formats associated with PDSCH transmissions to MTC UEs or PUSCHtransmissions from MTC UEs, reducing a PDCCH overhead associated withscheduling PDSCH transmissions to MTC UEs or PUSCH transmissions fromMTC UEs, and defining different coding methods for data transmitted toan MTC UE than for data transmitted from an MTC UE

The above information is presented as background information only toassist with an understanding of the present disclosure. No determinationhas been made, and no assertion is made, as to whether any of the abovemight be applicable as prior art with regard to the present invention.

SUMMARY OF THE INVENTION

Aspects of the present invention are to address at least theabove-mentioned problems and or disadvantages and to provide at leastthe advantages described below. Accordingly, an aspect of the presentinvention is to provide methods and apparatuses to design transmissionsmodes and respective DL Control Information (DCI) formats associatedwith PDSCH transmissions to MTC UEs or PUSCH transmissions from MTC UEs,reduce a PDCCH overhead associated with scheduling PDSCH transmissionsto MTC UEs or PUSCH transmissions from MTC UEs, and to define differentcoding methods for data transmitted to an MTC UE than for datatransmitted from an MTC UE.

In accordance with another aspect of the present invention, a method fora base station to schedule a conventional UE to transmit a first PUSCHand an MTC UE to transmit a second PUSCH. The method includestransmitting a first DCI format to the conventional UE informing of afirst set of IEs including a first HARQ process number IE represented bya first number of bits and transmitting a second DCI format to the MTCUE informing of a second set of IEs including a second HARQ processnumber IE represented by a second number of bits, wherein the secondnumber of bits is smaller than the first number of bits. The first setof IEs can further include a CS and OCC IE represented by a first numberof bits and indicating transmission parameters for a reference signal inthe first PUSCH and the second set of IEs can further include a CS andOCC IE represented by a second number of bits and indicatingtransmission parameters for a reference signal in the second PUSCH,wherein the second number of bits is smaller than the first number ofbits. The first set of IEs can further includes a FH IE represented byone bit and indicating whether or not the first PUSCH transmission is ata same part of a BW or at different parts of a BW during a UL TTI andthe second set of IEs does not include a FH IE.

In accordance with another aspect of the present invention, a method fora base station to schedule a conventional UE to receive a first PDSCHand an MTC UE to receive a second PDSCH is provided. The method includestransmitting a DCI format to the conventional UE informing of a firstset of IEs including a first HARQ process number IE represented by afirst number of bits and transmitting a second DCI format to the MTC UEinforming of a second set of IEs including a second HARQ process numberIE represented by a second number of bits, wherein the second number ofbits is smaller than the first number of bits including being equal tozero. The first set of IEs can further include a Redundancy Version (RV)IE represented by a first number of bits and indicating a RV for aretransmission of a data TB using IR and the second set of IEs does notinclude a RV IE. The first set of IEs can further include a SRS requestIE represented by one bit and the second set of IEs can further includea SRS request IE represented by more than one bit and indicating whetheror not the second UE transmits a SRS using a set of transmissionparameters from more than one configured sets of transmissionparameters. The first set of IEs can further include a RA IE indicatinga transmission BW with granularity of one RB and the second set of IEscan include a RA IE indicating a transmission BW with granularity of afraction of a RB. The first set of IEs can further include a DAI IEinforming the first UE of a number of PDSCH transmissions within anumber of DL TTIs and the second set of IEs does not include a DAI IE.The first DCI format can be one of two different DCI formatscorresponding to two different TMs for the first PDSCH and the secondDCI format is fixed for a respective fixed TM for the second PDSCH.

In accordance with another aspect of the present invention, a method foran MTC UE to transmit a PUSCH or receives a PDSCH is provided. Themethod includes detecting a first DCI format or by detecting a secondDCI format wherein the first DCI format includes CRC bits that arescrambled by a first RNTI assigned to the MTC UE by a base station andthe second DCI format includes CRC bits that are scrambled by a secondRNTI assigned to the MTC UE by the base station, and wherein the firstDCI format has a same size as the second DCI format. The second DCIformat can further contain a bit-map of X bits, the MTC UE is assignedone of the X bits, and the MTC UE transmits a PUSCH or receives a PDSCHif the assigned bit has a predetermined value. The second DCI formatfurther includes an IE including one bit and indicating whether itschedules a PUSCH transmission or a PDSCH reception. The MTC UE furtherdetermines a frequency resource to transmit a PUSCH or to receive aPDSCH, or further determines a resource to receive or transmit arespective HARQ-ACK signal, based on a sum of bits values located in thebit-map prior to the bit assigned to the MTC UE. The first DCI formatcan schedule either an initial transmission or a retransmission of adata TB and the second format can schedule only an initial transmissionof a data TB.

In accordance with another aspect of the present invention, a method foran MTC UE to transmit first data in a PUSCH and receives second data ina PDSCH is provided. The method includes encoding the first data using aturbo encoder and transmitting the encoded first data in the PUSCH, andreceiving the PDSCH and decoding encoded second data using aconvolutional decoder to obtain the second data, wherein a maximum sizeof the first data is larger than a maximum size of the second data. Themaximum number of frequency resources for a PUSCH transmission can belarger than a maximum number of frequency resources for a PDSCHreception.

In accordance with another aspect of the present invention, a method fora base station to schedule a first User Equipment (UE) from a firstclass of UEs to transmit a first Physical Uplink Shared CHannel (PUSCH)and a second UE from a second class of UEs to transmit a second PUSCH isprovided. The method includes transmitting a first Downlink ControlInformation (DCI) format to the first UE, wherein the first DCIcomprises a first set of Information Elements (IEs) including a firstHybrid Automatic Repeat reQuest (HARQ) process number IE represented bya first number of bits, and transmitting a second DCI format to thesecond UE, wherein the second DCI comprises a second set of IEsincluding a second HARQ process number IE represented by a second numberof bits, wherein the second number of bits is smaller than the firstnumber of bits.

In accordance with another aspect of the present invention, a method fora base station to schedule a first User Equipment (UE) from a firstclass of UEs to receive a first Physical Downlink Shared CHannel (PDSCH)and a second UE from a second class of UEs to receive a second PDSCH isprovided. The method includes transmitting a first Downlink ControlInformation (DCI) format to the first UE, wherein the first DCIcomprises a first set of Information Elements (IEs) including a firstHybrid Automatic Repeat reQuest (HARQ) process number IE represented bya first number of bits, and transmitting a second DCI format to thesecond UE, wherein the second DCI comprises a second set of IEsincluding a second HARQ process number IE represented by a second numberof bits, wherein the second number of bits is smaller than the firstnumber of bits including being equal to zero.

In accordance with another aspect of the present invention, a method fora User Equipment (UE) to transmit first data in a Physical Uplink SharedCHannel (PUSCH) and to receive second data in a Physical Downlink SharedCHannel (PDSCH) is provided. The method includes at least one ofdetecting by the UE a first Downlink Control Information (DCI) formatand detecting a second DCI format, wherein the first DCI format includesCyclic Redundancy Check (CRC) bits that are scrambled by a first RadioNetwork Temporary Identifier (RNTI) assigned to the UE by a base stationand the second DCI format includes CRC bits that are scrambled by asecond RNTI assigned to the UE by the base station, and wherein thefirst DCI format has a same size as the second DCI format, and at leastone of transmitting the PUSCH and receiving the PDSCH in response todetecting at least one of the first DCI format and the second DCIformat.

In accordance with another aspect of the present invention, a method fora User Equipment (UE) to transmit first data in a Physical Uplink SharedCHannel (PUSCH) and to receive second data in a Physical Downlink SharedCHannel (PDSCH). The method includes encoding the first data using aturbo encoder and transmitting the encoded first data in the PUSCH, andreceiving the PDSCH and decoding encoded second data using aconvolutional decoder to obtain the second data, wherein a maximum sizeof the first data is larger than a maximum size of the second data.

In accordance with another aspect of the present invention, a UserEquipment (UE) apparatus for transmitting a Physical Uplink SharedCHannel (PUSCH) or for receiving a Physical Downlink Shared CHannel(PDSCH) is provided. The UE includes a detector for detecting at leastone of a first Downlink Control Information (DCI) format and a secondDCI format, wherein the first DCI format includes Cyclic RedundancyCheck (CRC) bits that are scrambled by a first Radio Network TemporaryIdentifier (RNTI) assigned to the UE apparatus by a base station,wherein the second DCI format includes CRC bits that are scrambled by asecond RNTI assigned to the UE apparatus by the base station, andwherein the first DCI format has a same size as the second DCI format,and at least one of a transmitter for transmitting the PUSCH or and areceiver for receiving the PDSCH in response to detecting the first DCIformat or the second DCI format.

In accordance with another aspect of the present invention, a UserEquipment (UE) apparatus for transmitting first data in a PhysicalUplink Shared CHannel (PUSCH) and for receiving second data in aPhysical Downlink Shared CHannel (PDSCH) is provided. The UE includes anencoder for encoding the first data using a turbo encoder, a transmitterfor transmitting the encoded first data in the PUSCH, a receiver forreceiving the PDSCH, and a decoder for decoding encoded second data inthe received PDSCH using a convolutional decoder to obtain the seconddata, wherein a maximum size of the first data is larger than a maximumsize of the second data.

Other aspects, advantages, and salient features of the invention willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of the presentinvention will be more apparent from the following description taken inconjunction with the accompanying drawings, in which:

FIG. 1 is a diagram illustrating a structure for a DownLink (DL)Transmission Time Interval (TTI) according to the related art;

FIG. 2 is a diagram illustrating Enhanced Physical DL Control CHannelEPDCCH transmissions in a DL subframe according to the related art;

FIG. 3 is a diagram illustrating a DeModulation Reference Signal (DMRS)structure in a Resource Block RB over a DL TTI according to the relatedart;

FIG. 4 is a diagram illustrating an encoding and transmission processfor a DL Control Information (DCI) format according to the related art;

FIG. 5 is a diagram illustrating a reception and decoding process for aDCI format according to the related art;

FIG. 6 is a diagram illustrating a Physical Uplink Shared CHannel(PUSCH) transmission structure over an UpLink (UL) TTI according to therelated art;

FIG. 7 is a diagram illustrating a Physical Uplink Control CHannel(PUCCH) structure for Hybrid Automatic Repeat reQuest-ACKnowledgment(HARQ-ACK) signal transmission according to the related art;

FIG. 8 is a diagram illustrating a transmitter for a Zadoff-Chu (ZC)sequence according to the related art;

FIG. 9 is a diagram providing a detection performance for a Tail-BitingConvolutional Code (TBCC) and for a turbo code according to the relatedart;

FIG. 10 is a diagram illustrating decoding operations at a Machine TypeCommunication (MTC) User Equipment (UE) according to an exemplaryembodiment of the present invention;

FIG. 11 is a diagram illustrating an interpretation of a ResourceAllocation (RA) Information Element (IE) in DCI format 0_MTC and DCIformat 1A_MTC based on a configuration of a resource granularityaccording to an exemplary embodiment of the present invention;

FIG. 12 is a diagram illustrating a process for group scheduling of MTCUEs according to an exemplary embodiment of the present invention;

FIG. 13 is a diagram illustrating a process for an MTC UE in a group ofMTC UEs to determine its assigned resources in response to detecting aDCI format with an MTC-group-Radio Network Temporary Identifier (RNTI)according to an exemplary embodiment of the present invention;

FIG. 14 is a diagram illustrating a first determination of a PUCCHresource by an MTC UE for HARQ-ACK signal transmission in response to adetection of a DCI format with Cyclic Redundancy Check (CRC) scrambledwith an MTC-group-RNTI according to an exemplary embodiment of thepresent invention;

FIG. 15 is a diagram illustrating a second determination of a PUCCHresource for HARQ-ACK signal transmission by an MTC UE in response to adetection of a DCI format with CRC scrambled with an MTC-group-RNTIaccording to an exemplary embodiment of the present invention;

FIG. 16 is a diagram illustrating a first determination of a PHICHresource by an MTC UE for HARQ-ACK signal reception in response to aPUSCH transmission scheduled by a detected DCI format with CRC scrambledwith an MTC-group-RNTI according to an exemplary embodiment of thepresent invention;

FIG. 17 is a diagram illustrating a second determination of a PhysicalHybrid-ARQ Indicator CHannel (PHICH) resource by an MTC UE for HARQ-ACKsignal reception in response to a PUSCH transmission scheduled by adetected DCI format with CRC scrambled with an MTC-group-RNTI accordingto an exemplary embodiment of the present invention; and

FIG. 18 is a diagram illustrating a selection of an encoding operationfor data transmission in a Physical Downlink Shared CHannel (PDSCH) toan MTC UE and an encoding operation for data transmission in a PUSCHfrom an MTC UE according to an exemplary embodiment of the presentinvention.

Throughout the drawings, it should be noted that like reference numbersare used to depict the same or similar elements, features, andstructures.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of exemplaryembodiments of the invention as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the embodiments described hereincan be made without departing from the scope and spirit of theinvention. In addition, descriptions of well-known functions andconstructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of theinvention. Accordingly, it should be apparent to those skilled in theart that the following description of exemplary embodiments of thepresent invention is provided for illustration purpose only and not forthe purpose of limiting the invention as defined by the appended claimsand their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

Additionally, although the exemplary embodiments of the presentinvention will be described with reference to Orthogonal FrequencyDivision Multiplexing (OFDM), exemplary embodiments of the presentinvention are also applicable to all Frequency Division Multiplexing(FDM) transmissions in general and to Discrete Fourier Transform(DFT)-spread OFDM in particular. Moreover, although the exemplaryembodiments of the present invention will be described with reference toPhysical DownLink Control CHannel (PDCCH), unless explicitly noted,exemplary embodiments of the present invention are also applicable forEnhanced Physical DownLink Control CHannel (EPDCCH).

The first exemplary embodiment of the present invention considers adesign of Downlink Control Information (DCI) formats for PhysicalDownlink Shared CHannel (PDSCH) transmissions to and Physical UplinkShared CHannel (PUSCH) transmissions from a Machine Type Communication(MTC) User Equipment (UE).

The first exemplary embodiment of the present invention considersmodifications to DCI format 0 and DCI format 1A used for conventionalUEs. The respective modified DCI formats will be referred to as DCIformat 0_MTC and DCI format 1A_MTC. One design objective is to determinenecessary IEs and their size in DCI format 0_MTC and DCI format 1A_MTCwhile considering reduced capabilities and operational characteristicsof MTC UEs in order to reduce an associated PDCCH signaling overhead.Another design objective is to minimize a number of PDCCH decodingoperations an MTC UE performs per subframe by designing DCI format 0_MTCand DCI format 1A_MTC to include a same number of bits.

For a design of DCI formats for MTC UEs, exemplary embodiments of thepresent invention incorporate principles described in the U.S. Pat.8,238,297 titled “METHOD AND SYSTEM FOR DIMENSIONING SCHEDULINGASSIGNMENTS IN A COMMUNICATION SYSTEM” in which a compact DCI format 0or a compact DCI format 1A is designed to serve a second class of UEs ina communication system in which the second class of UEs transmits PUSCHor receives PDSCH using a smaller BW or a smaller TBS than a first classof UEs.

DCI format 0_MTC incorporates attributes of smaller transmission BW orsmaller TBS of a compact DCI format 0 and includes one or moreadditional restrictions as described below.

Table 3 describes IEs included in DCI format 0_MTC for an FDD system.

TABLE 3 DCI Format 0_MTC for PUSCH Scheduling of an MTC IE Number ofBits Flag for DCI Format Differentiation 1 RA⌈log₂(N_(RB_MTC)^(UL)(N_(RB_MTC)^(UL) + 1)/2)⌉ MCS and RV 3 FH Flag 0NDI 1 HARQ Process Number 0-3 TPC Command for PUSCH 2 CS and OCC Indexn_(DMRS) 0-1 CSI Request 1 SRS Request 1 Padding Bits for 0=1A 0 RNTI 16Total (FDD) 30-34

A 1-bit flag IE provides differentiation between DCI format 0_MTC andDCI format 1A_MTC because, as for DCI format 0 and DCI format 1A,exemplary embodiments of the present invention consider that these twoDCI formats have a same size.

An RA IE can be reduced in scope to address only a PUSCH transmission BWfor an MTC UE, expressed in a number of

N_(RB_MTC)^(UL)

UL RBs, which can be smaller than a PUSCH transmission BW for aconventional UE.

An MCS and RV IE can be reduced from 5 bits to, for example, 3 bits asan MCS corresponding to QAM16 or QAM64 may not be supported by MTC UEsor as an MCS granularity can be smaller than for conventional UEs.Moreover, the RV may be always assumed to be zero as, for HARQretransmissions of a data TB, if such retransmissions are supported bythe physical layer, IR has similar performance with chase combining forsmall data TBs.

A FH flag IE can be removed from DCI format 0_MTC because, if a small ULBW is used by MTC UEs, a performance difference between a format havingan FH and a format having no FH for PUSCH transmissions will be small. APUSCH transmission type (e.g., with or without FH) can be a defaultoperational characteristic or the PUSCH transmission type can beconfigured to an MTC UE by higher layer signaling. For example, if afrequency diversity offered by FH is small, a PUSCH transmission can bemade without FH to obtain better channel estimation from possible DMRSaveraging across slots of a PUSCH subframe as illustrated in FIG. 6 .Also, as MTC UEs typically have low mobility, higher layer signaling maybe used to configure whether FH is used or not for a PUSCH transmission.

A HARQ process number IE can be included if multiple HARQ processes aresupported for PUSCH transmissions from MTC_UEs. If so, a number of HARQprocesses for MTC UEs may be smaller than for conventional UEs, in orderto reduce buffering requirements and therefore reduce Digital Base-Band(DBB) complexity, and can be represented with a smaller number of bitsfor MTC UEs, such as 2 bits for 4 HARQ processes, than for conventionalUEs (e.g., 3 bits for 8 HARQ processes).

A CS and OCC index IE, n_(DMRS), can be either removed from DCI format0_MTC or be reduced in scope. The CS and OCC index IE, n_(DMRS), can beeither removed from DCI format 0_MTC or be reduced in scope because if aPUSCH transmission BW includes only a few RBs, using spatialmultiplexing for PUSCH transmissions from different MTC UEs does notprovide meaningful UL throughput gains and therefore a large range forn_(DMRS) to index a PHICH resource in response to each PUSCHtransmission is not needed. Therefore, n_(DMRS) may be either omitted orn_(DMRS) may be represented by a single bit rather than 3 bits asconventional UEs use. If n_(DMRS) is omitted, a CS and OCC value for aDMRS transmission may be either configured by higher layer signaling orbe set to a default value, such as CS 0 and OCC {1, 1}.

A NDI IE, a TPC command IE, a CSI request IE, and a SRS request IE, canbe included in DCI format 0_MTC as in DCI format 0.

For DCI format 1A_MTC, as for DCI format 0_MTC, exemplary embodiments ofthe present invention consider a reduced DBB capability of an MTC UE andincorporate respective attributes while designing a same size for DCIformat 1A_MTC and DCI format 0_MTC. Relative to DCI format 1A, DCIformat 1A_MTC includes one or more additional restrictions as they aresubsequently described.

Table 4 describes IEs included in DCI format 1A_MTC for a FrequencyDivision Duplex (FDD) system.

TABLE 4 DCI Format 1A_MTC for PDSCH Scheduling of an MTC IE Number ofBits Flag for 0_MTC/1A_MTC 1 RA⌈log₂(N_(RB_MTC)^(DL)(N_(RB_MTC)^(DL) + 1)/2)⌉ MCS 3Distributed/Localized Transmission Flag 0 NDI 1 RV 0 HARQ Process Number0-3 TPC Command for PUCCH 0-2 CSI Request 0-2 SRS Request 1-2 PaddingBits for 0=1A ≥0 RNTI 16 Total 27-35

A 1-bit flag IE provides differentiation between DCI format 0_MTC andDCI format 1A_MTC.

A RA IE can be reduced in scope to address only a PDSCH transmission BWfor an MTC UE, expressed in a number of

N_(RB_MTC)^(DL)

DL RBs, which can be smaller than a PDSCH transmission BW for aconventional UE.

An MCS IE can be reduced from 5 bits to 3 bits as MCS corresponding toQAM16 or QAM64 modulations may not be supported by MTC UEs or an MCSgranularity may be reduced relative to conventional UEs. As for DCIformat 0_MTC, a subset of MCS corresponding to QPSK for a conventionalUE may only be supported (a highest MCS corresponding to QPSK is alwaysincluded).

A distributed or localized PDSCH transmission flag IE can be removedfrom DCI format 1A_MTC as, if a total available PDSCH transmission BWfor MTC UEs is only a few RBs, a performance difference between the twoPDSCH transmission types (e.g., distributed or localized) will be smallin practice. Whether a PDSCH transmission is distributed or localizedcan be a default operational choice or can be configured to an MTC UE byhigher layer signaling, for example depending on an MTC UE’s mobility.Also, if PDSCH demodulation is based on a CRS, a PDSCH transmission canbe distributed because there is no penalty to channel estimationaccuracy. If PDSCH demodulation is based on DMRS, a PDSCH transmissioncan be localized to enable averaging of DMRS across the two slots persubframe.

A RV IE can be removed from DCI format 1A_MTC as processing of a data TBfor HARQ retransmissions may be based on chase combining. Alternatively,in order to minimize buffering requirements at an MTC UE, physical layerHARQ retransmissions may not be supported.

A HARQ process number IE can be included if multiple asynchronous HARQprocesses are supported for PDSCH transmissions to an MTC_UE. Otherwise,a HARQ process number IE is not included. As for PUSCH transmissions toMTC UEs, the number of HARQ processes for PDSCH transmissions can besmaller than for conventional UEs in order to reduce bufferingrequirements and therefore reduce DBB complexity. The HARQ processnumber IE can be represented with a smaller number of bits for MTC UEs,such as 2 bits for 4 HARQ processes, than for conventional UEs (3 bitsfor 8 HARQ processes). Moreover, a number of HARQ processes for PDSCHtransmissions can be different from a number of HARQ processes for PUSCHtransmissions. For example, considering asymmetric traffic requirementsof MTC UEs (more UL traffic than DL traffic), more HARQ processes can besupported for PUSCH transmissions.

A TPC command IE can be maintained using 2 bits or, if HARQ-ACKsignaling in a PUCCH is not supported, the TPC command IE can becompletely removed.

A NDI IE and a SRS request IE can be included in DCI format 1A_MTC as inDCI format 1A.

As a DCI format 1A_MTC will be smaller than a DCI format 0_MTC, assumingat least same reductions in a number of bits for IEs common to these twoDCI formats, and as it is desirable to maintain a same size for DCIformat 0_MTC and DCI format 1A_MTC in order to avoid increasing a numberof PDCCH decoding operations at an MTC UE, padding bits are necessaryfor DCI format 1A_MTC to make its size same as that of DCI format 0_MTC.

As padding bits do not carry information, the padding bits can beexchanged for additional functionality in DCI format 1A_MTC relative toDCI format 1A. For example, a CSI request IE can be included in DCIformat 1A_MTC although the CSI request IE is not included in DCI format1A. One or more PUCCH resources can be configured to an MTC UE by higherlayer signaling for CSI transmission triggered by DCI format 1A_MTC. ACSI request IE value determines whether an MTC UE should report CSI and,if so, which PUCCH resource to use for a respective transmission. A SRSrequest may also be expanded from one bit to two bits in order toprovide more flexibility for resources, such as a CS or a BW location,used by a SRS transmission.

Unlike DCI format 1A which is associated with PDSCH demodulation using aCRS, DCI format 1A_MTC may also support PDSCH demodulation using a DMRSif a DL operation for an MTC UE is DMRS based.

As a TBS for MTC UEs can be as small as a few tens of bits, a BWgranularity of one RB for PDSCH transmissions to an MTC UE or for PUSCHtransmissions from an MTC UE may be too large. Reducing a BW granularityto half RB can improve PDSCH or PUSCH spectral efficiency by betteraligning a TBS to allocated resources. A half RB granularity can beaccommodated by DCI format 0_MTC and DCI format 1A_MTC by simply setting

N_(RB_MTC)^(UL) = 2 ⋅ N_(RB_MTC)^(UL)

in Table 3 and

N_(RB_MTC)^(DL) = 2 ⋅ N_(RB_MTC)^(DL)

in Table 4.

Although DCI format 0_MTC in Table 3 and DCI format 1A_MTC in Table 4assume an FDD system, the same IEs are also applicable for a TDD system.Regarding the two additional IEs of DCI formats for conventional UEs inTDD systems, namely the Downlink Assignment Index (DAI) IE and the ULindex IE, their necessity for MTC UEs can be reconsidered. Ascommunication with MTC UEs is typically more UL than DL intensive, PUSCHtransmissions from MTC UEs are more frequent than PDSCH transmissions toMTC UEs that usually provide higher layer control signaling information.Therefore, MTC UEs do not typically require multiple PDSCH transmissionswithin a bundling window and a DAI IE may be omitted from DCI format0_MTC and DCI format 1A_MTC. The conventional UL index IE should beincluded in DCI format 0_MTC as TDD UL-DL configurations aiming toprimarily support MTC UEs may have more UL subframes than DL subframesper frame. Two additional padding bits can be included in DCI format1A_MTC to maintain a same size with DCI format 0_MTC when an UL index IEof 2 bits is included in DCI format 0_MTC.

A number of PDCCH decoding operations an MTC UE performs for eachControl Channel Element (CCE) AL can be configured by a NodeB throughhigher layer signaling. Alternatively, or prior to a configuration byhigher layer signaling, a fixed number of PDCCH decoding operations forrespective CCE ALs can be supported in order to enable detection of aDCI format scheduling PDSCH before any higher layer signaling can beprovided. For example, an MTC UE may perform 2 decoding operations forAL of 4 CCEs and 2 decoding operations for AL of 8 CCEs to detect a DCIformat in a PDCCH that schedules a PDSCH with configuration informationafter the MTC UE performs initial system access. Additionally, ascommunication with MTC UEs is more UL than DL intensive, if a size of aDCI format scheduling PUSCH is different than a size of a DCI formatscheduling PDSCH then, unlike conventional UEs, an MTC UE may perform alarger number of decoding operations for DCI formats scheduling PUSCHthan for DCI formats scheduling PDSCH.

FIG. 10 is a diagram illustrating decoding operations at an MTC UEaccording to an exemplary embodiment of the present invention.

Referring to FIG. 10 , during an initial access process to a NodeB, anMTC UE performs a first fixed number of PDCCH decoding operations perrespective CCE AL for a first set of CCE ALs in step 1010. For example,the MTC UE performs a first fixed number of PDCCH decoding operationsper respective CCE AL for a first set of CCE ALs as specified in theoperation of the communication system. After detecting a PDCCHscheduling a PDSCH conveying configuration information as part of theinitial access process, in step 1020 the MTC UE is either configured bya NodeB a number of PDCCH decoding operations for each CCE AL for asecond set of CCE ALs or uses a second fixed number of PDCCH decodingoperations per respective CCE AL for a second set CCE ALs which can bedifferent than the PDCCH decoding operations used during the initialaccess process. The second fixed number of PDCCH decoding operations perrespective CCE AL and the second set CCE ALs can also be differentrelative to respective ones for conventional UEs while the first fixednumber of PDCCH decoding operations per respective CCE AL and the firstset CCE ALs can be same for MTC UEs and conventional UEs. An MTC UEsubsequently performs a number of decoding operations for each CCE AL instep 1030.

Unlike a conventional UE which is assumed to decode at least a DL TMdependent DCI format having a different size than DCI format 0/1A,communication with an MTC UE can be based only on DCI format 0_MTC andDCI format 1A_MTC having a same size. Consequently, an MTC UE performsat most half a number of PDCCH decoding operations that a conventionalUE performs.

As Digital Base-Band (DBB) complexity is dominated by the receiver andas communication with MTC UEs is more UL than DL intensive, PUSCHtransmissions from MTC UEs may be over a larger BW than PDSCHtransmissions to MTC UEs. As a result, having a same size for DCIformats 0_MTC and 1A_MTC is practically not possible without imposingadditional restrictions to a RA IE of DCI format 0_MTC. In this case,exemplary embodiment of the present invention considers that a resourceunit in DCI format 0_MTC can be different than a resource unit in DCIformat 1A_MTC. For example, if a total available UL BW is 25 RBs and atotal available DL BW is 6 RBs, a same size for a RA IE can be achievedif a resource unit in DCI format 0_MTC is 4 RBs (for a maximum ULresource allocation of 24 RBs) and a resource unit in DCI format 1A_MTCis 1 RB.

FIG. 11 is a diagram illustrating an interpretation of a ResourceAllocation (RA) IE in DCI format 0_MTC and DCI format 1A_MTC based on aconfiguration of a resource granularity according to an exemplaryembodiment of the present invention.

Referring to FIG. 11 , in step 1110, an MTC UE is configured by a NodeBthrough higher layer signaling a resource unit of

Q_(RB_MTC)^(DL)

RBs for PDSCH transmissions and of

Q_(RB_MTC)^(UL)

RBs for PUSCH transmissions. Upon reception of a DCI format 0_MTCindicating allocation of

P_(RB_MTC)^(UL)

resource units, in step 1120, an MTC UE transmits a PUSCH over

Q_(RB_MTC)^(UL) ⋅ P_(RB_MTC)^(UL) RBs.

Similarly, upon reception of a DCI format 1A_MTC indicating allocationof

P_(RB_MTC)^(UL)

resource units, in step 1130, an MTC UE transmits a PUSCH over

Q_(RB_MTC)^(DL) ⋅ P_(RB_MTC)^(DL)

RBs 1130. Either a DL resource unit

Q_(RB_MTC)^(DL)

or a UL resource unit

Q_(RB_MTC)^(UL)

can be a fraction of a RB or a multiple of a RB.

In addition to a capability of an MTC UE to have a PUSCH transmission BWlarger than a PDSCH reception BW, a PUSCH transmission may also use alarger TBS or a higher MCS than a PDSCH transmission uses. Then, eitheran MCS IE in DCI format 0_MTC may have a coarser granularity than an MCEIE in DCI format 1A_MTC or one additional bit may be included in an MCSIE in DCI format 0_MTC.

The second exemplary embodiment of the present invention considersscheduling for a group of MTC UEs using a single DCI format which canschedule either PDSCH or PUSCH transmissions to or from, respectively,multiple MTC UEs.

An MTC UE can be configured both with an MTC-UE- Radio Network TemporaryIdentifier (RNTI) and with an MTC-group-RNTI. A size of a DCI formatscheduling PDSCH or PUSCH for a group of MTC UEs is designed to be thesame as a size of a DCI format scheduling PDSCH or PUSCH, respectively,for an individual MTC UE. This constraint avoids increasing a number ofPDCCH decoding operations for an MTC UE due to support of groupscheduling and therefore avoids increasing a respective DBB receivercomplexity. In one example, in order to adapt to traffic variations, aNodeB may decide to simultaneously (re)-configure to a group of MTC UEs,by higher layer signaling in respective PDSCHs, parameters fortransmissions or receptions of various signals such as UL controlsignals, SRS, and so on. In another example, based on a Buffer StatusReport (BSR) from some MTC UEs (not necessarily in a same subframe) in agroup of MTC UEs for delay non-sensitive traffic such as metering, aNodeB may perform group scheduling of respective PUSCH transmissionsfrom a group of MTC UEs.

In order to provide efficient support for group scheduling of MTC UEswhile fulfilling a constraint for a respective DCI format to have a samesize as a DCI format for individual scheduling of an MTC UE (either forPDSCH or for PUSCH transmission), a DCI format for group scheduling ofMTC UEs should provide less flexibility, including no flexibility, indynamically setting values of IEs included in a DCI format scheduling anindividual MTC UE.

A NodeB has freedom to determine whether to use a DCI format with CRCscrambled by an MTC-UE-RNTI or with an MTC-group-RNTI. A determinationby a NodeB can be based on considerations such as a DL control overhead(e.g., group scheduling is advantageous), an optimization for spectralefficiency of each PDSCH or PUSCH transmission (e.g., individual MTC UEscheduling is advantageous), a traffic type from each MTC UE (e.g.,individual scheduling is advantageous for delay sensitive traffic whilegroup scheduling is advantageous otherwise), a BSR from each MTC UE(e.g., individual scheduling may be used if a RA size associated withgroup scheduling is not appropriate), and so on.

A DCI format scheduling a group of MTC UEs (UEs assigned a sameMTC-group-RNTI) should also be able to identify scheduled MTC UEs as notall MTC UEs may need to receive PDSCH or transmit PUSCH. Otherwise, ifan MTC UE always assumes that it is scheduled a PDSCH or a PUSCH when itreceives a DCI format with an MTC-group-RNTI, a respective waste of DLor UL resources may occur in order to maintain robust system operation.Therefore, a DCI format scheduling a group of MTC UEs should include anMTC UE identification IE in a form of a bit-map indicating which MTC UEsin a group of MTC UEs are actually being scheduled. For this MTC UEidentification IE, a one-to-one correspondence exists between each MTCUE, in a group of MTC UEs, and a binary element in a bit-map. Thiscorrespondence is represented by an MTC-index IE which, together with aconfiguration to an MTC UE for group scheduling by an MTC-group-RNTI, isinformed by a NodeB to an MTC UE in advance through higher layersignaling.

FIG. 12 is a diagram illustrating a process for group scheduling of MTCUEs according to an exemplary embodiment of the present invention.

Referring to FIG. 12 , in step 1210, a NodeB first configures an MTC UEwith an MTC-group-RNTI and with a respective MTC-index 1212 in an MTC UEidentification IE 1214 included in a DCI format with CRC scrambled by arespective MTC-group-RNTI. Thereafter, in step 1220, an MTC UE detects aDCI format with CRC scrambled with an MTC-group-RNTI assigned to the MTCUE. Subsequently, an MTC UE examines an MTC identification IE value inits assigned MTC-index 1230. For example, the MTC UE determines whetherthe MTC identification IE is set to 1. If this value is set to 1, theprocess proceeds to step 1240 in which an MTC UE receives PDSCH ortransmits PUSCH depending on a respective type of the DCI format.Otherwise, if the value is not set to 1, the process proceeds to step1250 in which an MTC UE disregards a DCI format.

Under an objective of having a same size for a DCI format scheduling anindividual MTC UE and a DCI format scheduling a group of MTC UEs, atreatment of IEs in the former DCI format is now considered in a designof the latter DCI format.

A 1-bit DCI format differentiation flag IE indicates whether a DCIformat is applicable to PDSCH group scheduling or PUSCH groupscheduling. A functionality of this IE is same as for individual MTC UEscheduling with DCI format 0_MTC or DCI format 1A_MTC. An alternative isto configure a UE with a first MTC-group-RNTI for PDSCH group schedulingand with a second MTC-group-RNTI for PUSCH group scheduling or toconfigure a UE for only PDSCH group scheduling or for only PUSCH groupscheduling.

An RA IE is not included in a DCI format scheduling a group of MTC UEs.Instead, resources allocated to each MTC UE in a group are predeterminedand, although not necessary, all MTC UEs in a same group can have a samesize of resources. This leads to a simpler implementation because an MTCUE in a group does not need additional explicit signaling to derive itsallocated resources. A resource allocation unit MTC_(group_RA-unit) canbe a multiple or a sub-multiple of a RB and can be informed to an MTC UEby a NodeB through higher layer signaling or be predetermined in theoperation of a communication system. Available resources may start froma predetermined resource MTC_(group_RA_first), which may be informed toan MTC UE by higher layer signaling or be implicitly determined, andcontinue in a sequential order in steps of a resource allocation unitMTC_(group_RA-unit). An MTC UE determines a starting point of itsassigned MTC_(group_RA-unit) RBs for PDSCH reception or PUSCHtransmission, MTC_(RA-start), based on a sum of elements in an MTC UEidentification IE located prior to a location (MTC-index) configured tothe MTC UE, MTC_(run_sum), and MTC_(RA-start) = MTC_(group_RA_first) +MTC_(run_sum) · MTC_(group_RA-unit).

For example, for a DCI format performing PDSCH scheduling to a group of4 MTC UEs, a first MTC UE with bit-map value (MTC-index value) of 1 maybe allocated a RB with a lowest index (MTC_(group_RA-unit) is 1 RB,MTC_(group_RA_first) = 0, and MTC_(run_sum) = 0), a second MTC UE withbit-map value of 1 may be allocated a RB with a second lowest index

(MTC_(run_sum) = 1),

and so on. In a case in which E-CCHs are used, respective RBs may beexcluded by MTC UEs in a determination of their respective resources andMTC_(group_RA_first) may still be implicitly determined by excludingresources allocated to a transmission of E-CCHs.

FIG. 13 is a diagram illustrating a process for an MTC UE in a group ofMTC UEs to determine its assigned resources in response to detecting aDCI format with an MTC-group-RNTI according to an exemplary embodimentof the present invention.

Referring to FIG. 13 , in step 1310, an MTC UE configured with anMTC-group-RNTI and with an MTC-index (location) in an MTC UEidentification IE contained in a DCI format with CRC scrambled by anMTC-group-RNTI, as described in FIG. 12 , detects a respective PDCCH anddetermines that an MTC UE identification IE value in its assignedMTC-index is equal to 1. Thereafter, in step 1320, an MTC UE alsodetermines that an MTC UE identification IE includes 2 other values of1, 1322 and 1324, located prior to its assigned MTC-index 1326

(MTC_(run_sum) = 2).

Based on a signaled or predetermined resource unit MTC_(group_RA-unit),an MTC UE determines its resource for PDSCH reception or for PUSCHtransmission starting at MTC_(RA-start) = MTC_(group_RA_first) + 2 ·MTC_(group) _(_RA-unit) and with a size of MTC_(group_RA-unit) RBs instep 1330.

A transmission type IE (distributed/localized transmission IE or FH flagIE) may not be included in a DCI format scheduling a group of MTC UEs.Instead, all transmissions may have a same type which can be eitherpredetermined in the operation of a communication system or beconfigured to each MTC UE in the group of MTC UEs by higher layersignaling. For example, all PDSCH transmissions may be distributed andall PUCCH transmissions may perform FH.

An MCS and RV IE for PUSCH transmission or an MCS IE for PDSCHtransmission may or may not be included in a DCI format scheduling agroup of MTC UEs. If an MCS and RV IE is not included, an MCS isconfigured to each MTC UE in a group of MTC UEs by higher layersignaling. For example, an MCS can be based on the long term SINR an MTCUE experiences in an UL channel or in a DL channel. If an MCS and RV IEis included, a number of respective bits can be reduced compared to anumber of bits in a DCI format scheduling an individual MTC UE, forexample from 3 to 2. At least in case of PUSCH transmissions, an RV isalways zero (e.g., only initial transmissions of a TB may be supportedby group scheduling as is subsequently discussed).

An NDI IE may not be included in a DCI format scheduling a group of MTCUEs and respective PDSCH or PUSCH transmissions can always be initialtransmissions. A reason for not supporting group scheduling forretransmissions of an HARQ process, if such retransmissions aresupported at the physical layer, is because of a much smaller likelihoodthat a predetermined group of MTC UEs will need such retransmissions.For example, if a DCI format schedules PDSCH transmissions to a group ofMTC UEs, a retransmission will only be needed for MTC UEs that did notcorrectly receive an initial PDSCH transmission and, for typical PDSCHerror rates, a retransmission is more likely to be needed for much fewerMTC UEs than ones having an initial transmission. A DCI formatscheduling an individual MTC UE can then be used for retransmissions ofan HARQ process, if such retransmissions are supported at the physicallayer.

An RV IE may not be included in a DCI format scheduling a group of MTCUEs for respective PDSCH transmissions for the same reasons as for notincluding an NDI IE as mentioned above.

A HARQ process IE may or may not be included in a DCI format schedulingPDSCH or PUSCH transmissions to or from, respectively, a group of MTCUEs. If a HARQ process IE is not included, a HARQ process number (e.g.,assuming that more than one HARQ process is supported) can be implicitlydetermined for example by linking a HARQ process to a subframe number(e.g., synchronous HARQ in both DL and UL).

A TPC command IE may or may not be included in a DCI format schedulingPDSCH or PUSCH transmissions to or from, respectively, a group of MTCUEs. If HARQ-ACK signaling is not supported for MTC UEs then, instead ofa TPC command, a DCI format can include an MCS for PDSCH or PUSCHtransmissions to or from, respectively, a group of MTC UEs. Linkadaptation is then performed based on MCS adaptation instead of poweradaptation (e.g., an MTC UE can assume a TPC command indicating no poweradjustment).

In another alternative, a TPC command IE including 1 bit is included ina DCI format scheduling PDSCH or PUSCH transmissions to or from,respectively, a group of MTC UEs. The 1-bit TPC command IE may indicate,for example, a power adjustment of {-1 1} dB instead of a poweradjustment of {-3, -1, 0 1} dB that can be supported by a 2-bit TPCcommand IE.

In another alternative, neither a TPC IE nor an MCS IE is included in aDCI format for PDSCH or PUSCH scheduling to a group of MTC UEs. In acase in which a negative TPC command would be needed, a consequence is asomewhat increased interference. In a case in which a positive TPCcommand would be needed, a consequence is a somewhat increased errorrate.

A CS and OCC Index IE, n_(DMRS), may not be included in a DCI formatscheduling a group of MTC UEs for PUSCH transmissions. Instead, all MTCUEs can use a same CS and OCC which can be either predetermined, such asfor example CS=0 and OCC={1, 1}, or can be configured by higher layersignaling. A resource for PHICH transmission, if any, can be derivedfrom a MTC_(run_) _(sum) value for a respective UE as described below.

A CSI request IE may not be included in a DCI format scheduling PUSCHtransmissions from a group of MTC UEs. As CSI feedback is associatedwith PDSCH scheduling, not all MTC UEs scheduled PUSCH transmissions mayneed to report CSI in respective PUSCHs. Alternatively, a DCI formatwith an MTC-UE-RNTI can be used or MTC UEs can be configured with aseparate MTC-group-RNTI triggering CSI feedback using PUSCH or PUCCH anda determination of transmission parameters can be similar to that ofdata in a PUSCH as it was previously described.

A SRS request IE may not be included in a DCI format scheduling PDSCHtransmissions to or PUSCH transmissions from a group of MTC UEs as notall MTC UEs may need to also transmit SRS. Alternatively, a DCI formatwith an MTC-UE-RNTI can be used or MTC UEs can be configured with aseparate MTC-group-RNTI triggering SRS transmission with parameterspreviously configured by a NodeB through higher layer signaling for eachMTC UE in a group of MTC UEs.

Therefore, a DCI format scheduling a group of MTC UEs can include only arespective MTC-group-RNTI and an MTC UE identification IE (bit-map)without including any IEs provided by a DCI format scheduling anindividual MTC UE. Alternatively, a DCI format scheduling a group of MTCUEs can also include a minimal number of IEs provided by a DCI formatscheduling an individual MTC UE such as an MCS IE or a TPC IE.

Table 5 provides contents for a DCI format with CRC scrambled by anMTC-group-RNTI scheduling PDSCH transmissions to or PUSCH transmissionsfrom a group of MTC UEs under previously discussed alternatives forincluded IEs. A size of a DCI format scheduling a group of MTC UEs issame as a size of a DCI format scheduling an individual MTC UE andassumed to be bits.

TABLE 5 DCI Formats for Group Scheduling of MTC UEs IE Group DCI Format-Option 1 Group DCI Format -Option 2 Flag for DL/UL Scheduling 1 1 MTCUE identification Q - 17 ⌊(Q − 17)/(I + 1)⌋ Additional IEs (bits per MTCUE) - I Padding Bits - Q − 17 − ⌊(Q − 17)/(8 + 1)⌋ ⋅ (I + 1)MTC-group-RNTI 16 16 Total Q Q

If a DCI format scheduling a group of MTC UEs includes only anMTC-group-RNTI/CRC and a flag for distinguishing between PDSCH andPUSCH, a maximum number of MTC UEs in a group is Q - 17. For example,for Q = 29, a group may include up to 12 MTC UEs.

If a DCI format scheduling a group of MTC UEs additionally includesother IEs, such as a TPC IE or an MCS IE, corresponding to I bits perMTC UE, a maximum number of MTC UEs in a group is

⌊(Q − 17)/(I + 1)⌋.

For example, for I = 2 and Q = 29, a group can include up to 4 MTC UEs.A number of IEs included in a DCI format scheduling an individual MTC UEthat are also included in a DCI format scheduling a group of MTC UEsshould be as small as possible even with some acceptable performancedegradation or loss of flexibility, as, otherwise, a number of MTC UEsin a group can become too low for group scheduling to be useful.

An advantage of supporting a large number of MTC UEs by group schedulingis in allowing a NodeB scheduler to address any subset of these UEs witha single DCI format, thereby improving scheduler flexibility withouttransmitting multiple DCI formats and incurring a correspondingsignaling overhead. For a total PDSCH BW or a total PUSCH BW includingabout 6 RBs (e.g., at least for DBB operation), a maximum of 10-12 MTCUEs may be scheduled per subframe (assuming a resource unit of half RB).Therefore, for group scheduling, both a DCI format being able to addressup to 12 MTC UEs (but not schedule all of the 12 MTC UEs) and a DCIformat being able to address 4 MTC UEs (and possibly schedule all of the4 MTC UEs) are applicable.

The second exemplary embodiment of the present invention so far assumedthat a DCI format scheduling PDSCH for an individual MTC UE has a samesize as a DCI format scheduling PUSCH for an individual UE as describedby the first exemplary embodiment of the present invention. This ishowever not a necessary condition for the second exemplary embodiment ofthe present invention for which an only condition is that a DCI formatscheduling a group of MTC UEs for PDSCH or PUSCH has a same size with aDCI format scheduling PDSCH or PUSCH for an individual MTC UE,respectively. If a size of a DCI format for PDSCH scheduling is not sameas a size of the DCI format for PUSCH scheduling, whether for anindividual MTC UE or for a group of MTC UEs, a flag IE fordifferentiating DL scheduling from UL scheduling is not needed.

An HARQ-ACK signal transmission from or to an MTC UE in response to areception of a PDSCH or a transmission of a PUSCH, respectively, throughgroup scheduling by a respective DCI format with CRC scrambled by anMTC-group-RNTI is subsequently considered. An objective is to provide atechnique for a communication system to support such HARQ-ACK signalingand for an MTC UE to derive a respective PUCCH or PHICH resource. APUCCH or PHICH resource determination, as described by Equation (2) andEquation (1), respectively, is assumed but any other reference resourcedetermination may apply.

If an MTC UE transmits an HARQ-ACK signal in response to a detection ofa DCI format with CRC scrambled by an MTC-group-RNTI, or in general inresponse to a detection of a DCI format associated with DL groupscheduling, exemplary embodiments of the present invention considersthat an MTC UE determines a PUCCH resource for HARQ-ACK signaltransmission based on its MTC_(run_sum) value as determined from an MTCUE identification IE included in the DCI format.

In a first approach, each MTC UE configured for PDSCH group schedulingand with an MTC-group-RNTI is also configured by higher layer signalinga set of PUCCH resources for HARQ-ACK signal transmission. A PUCCHresource for HARQ-ACK signal transmission from a first MTC UE, which isthe MTC UE for which a first bit in a bit-map of an MTC UEidentification IE is equal to one, may be determined as for aconventional UE and derived from the first CCE used to transmit a PDCCHconveying the DCI format as in Equation (2). A PUCCH resource forHARQ-ACK signal transmission from each remaining MTC UE with actualscheduling, as determined by an MTC UE identification IE, is determinedfrom a set of configured PUCCH resources based on a respectiveMTC_(run_sum) value.

FIG. 14 is a diagram illustrating a first determination of a PUCCHresource by an MTC UE for HARQ-ACK signal transmission in response to adetection of a DCI format with CRC scrambled with an MTC-group-RNTIaccording to an exemplary embodiment of the present invention.

Referring to FIG. 14 , in step 1410, an MTC UE detects a DCI format withMTC-group-RNTI and with MTC UE Identification IE value at its assignedMTC-index equal to 1. Thereafter, an MTC UE computes a respectiveMTC_(run_sum) in step 1420. In step 1430, the MTC UE examines its value.For example, the MTC determines whether MTC_(run_sum) = 0. If MTC_(run_)_(sum) = 0, the MTC UE determines a PUCCH resource for HARQ-ACK signaltransmission from a first CCE used to transmit a respective PDCCH instep 1440. Otherwise, if MTC_(run) _(_) _(sum) does not equal 0, thenthe MTC UE determines a PUCCH resource for HARQ-ACK signal transmissionto be a MTC_(run_sum) resource from a set of PUCCH resources configuredby a NodeB to the MTC UE through higher layer signaling in step 1450.

In a modification of the first approach, a PUCCH resource for HARQ-ACKsignal transmission from a first MTC UE with actual scheduling may alsobe determined from a set of configured PUCCH resources by associatingeach MTC_(run_sum) value with a configured PUCCH resource in anascending order starting from a MTC_(run_sum) value of 0.

In a second approach, all PUCCH resources may be implicitly derived froma first CCE used to transmit a PDCCH conveying a DCI format scheduling agroup of MTC UEs and a MTC_(run_sum) value for each scheduled MTC UE asdetermined by an MTC UE identification IE. In this case, it is up to aNodeB scheduler to avoid HARQ-ACK signal transmissions from multiple UEsusing a same PUCCH resource.

FIG. 15 is a diagram illustrating a second determination of a PUCCHresource for HARQ-ACK signal transmission by an MTC UE in response to adetection of a DCI format with CRC scrambled with an MTC-group-RNTIaccording to an exemplary embodiment of the present invention.

Referring to FIG. 15 , in step 1510, an MTC UE detects a DCI format witha CRC scrambled by an MTC-group-RNTI and with MTC UE Identification IEvalue at its assigned MTC-index equal to 1. Thereafter, in step 1520,the MTC UE computes a respective MTC_(run_sum) value. The MTC UEdetermines a PUCCH resource n_(PUCCH) for HARQ-ACK signal transmissionas n_(PUCCH) = n_(CCE) + MTC_(run_sum) + N_(PUCCH) in step 1530.

If a HARQ-ACK signal is transmitted by a NodeB to an MTC UE in responseto a PUSCH transmission scheduled by a DCI format with CRC scrambled byan MTC-group-RNTI, the MTC UE may also determine a respective PHICHresource based on a MTC_(run_sum) value as determined from an MTC UEidentification IE using similar approaches as for PUCCH resourcedetermination for HARQ-ACK signal transmission from the MTC UE.

In a first approach, PHICH resources for HARQ-ACK signal transmissionsto MTC UEs with PUSCH transmissions through group scheduling areconfigured by higher layer signaling. Each scheduled MTC UE determines arespective PHICH resource, from a configured set of resources, accordingto a one-to-one mapping between each configured PHICH resource and anMTC_(run_sum) value where a first configured PHICH resource is mapped to_(MTCrun_sum) = 0, a second configured PHICH resource is mapped toMTC_(run_sum)=1, and so on.

FIG. 16 is a diagram illustrating a first determination of a PHICHresource by an MTC UE for HARQ-ACK signal reception in response to aPUSCH transmission scheduled by a detected DCI format with CRC scrambledwith an MTC-group-RNTI according to an exemplary embodiment of thepresent invention.

Referring to FIG. 16 , in step 1610, an MTC UE detects a DCI format withMTC-group-RNTI and with MTC UE Identification IE value at its assignedMTC-index equal to 1. Thereafter, in step 1620, the MTC UE computes arespective MTC_(run_sum). In step 1630, the MTC UE determines a PHICHresource for HARQ-ACK signal reception to be the MTC_(run_sum) resourcefrom a set of PUCCH resources configured by a NodeB to the MTC UEthrough higher layer signaling where a first configured PHICH resourcemaps to MTC_(run_sum) = 0, a second configured PHICH resource maps toMTC_(run_sum) = 1, and so on.

In a second approach, PHICH resources for HARQ-ACK signal transmissionsto MTC UEs with PUSCH transmissions through group scheduling aredetermined from a first resource MTC_(RA-start) for a respective PUSCHtransmission. This is similar to a conventional approach for determininga PHICH transmission resource but n_(DMRS) may not exist and

I_(PRB RA)^(lowest_index)

is replaced by the MTC_(run_sum) which an MTC UE determines from an MTCUE identification IE.

FIG. 17 is a diagram illustrating a second determination of a PHICHresource by an MTC UE for HARQ-ACK signal reception in response to aPUSCH transmission scheduled by a detected DCI format with CRC scrambledwith an MTC-group-RNTI according to an exemplary embodiment of thepresent invention.

Referring to FIG. 17 , in step 1710, an MTC UE detects a DCI format withMTC-group-RNTI and with MTC UE Identification IE value at its assignedMTC-index equal to 1. Thereafter, in step 1720, the MTC UE computes therespective MTC_(run_sum). In step 1730, the MTC UE determines a PHICHresource n_(PHICH) for HARQ-ACK signal reception as

n_(PHICH) = f(MTC_(run_sum), N_(PHICH))⋅

The third exemplary embodiment of the present invention considers a dataencoding method in a PDSCH transmitted to an MTC UE and a data encodingmethod in a PUSCH transmitted from an MTC UE.

Unlike conventional UEs for which a TBS typically exceed about 70 bitsand a TC is always used, most data information payloads to MTC UEs areonly in the order of a few tens of bits. Moreover, considering a DBBreceiver complexity of an MTC UE, a convolutional decoder is preferableto a turbo decoder. Furthermore, an MTC UE already includesconvolutional decoders for PDCCH decoding. Therefore, unlike aconventional UE, a data TB transmitted in a PDSCH to an MTC UE may beencoded using a TBCC. A TBS transmitted from an MTC UE in a PUSCH istypically larger than a TBS transmitted to an MTC UE in a PDSCH and, asa turbo encoder complexity is much smaller than a turbo decodercomplexity, either a turbo encoder or a convolutional encoder may beused to encode data transmitted from an MTC UE. For a same or similarmaximum MCS of data transmitted in a PDSCH or in a PUSCH, a largermaximum TBS for data in a PUSCH than in a PDSCH implies a larger maximumsize of frequency resources for a PUSCH than for a PDSCH.

FIG. 18 is a diagram illustrating a selection of an encoding operationfor data transmission in a PDSCH to an MTC UE and an encoding operationfor data transmission in a PUSCH from n MTC UE according to an exemplaryembodiment of the present invention.

Referring to FIG. 18 , in step 1810, an MTC UE encodes a datainformation using a TC. In step 1820, the MTC UE decodes a datainformation using a TBCC. The reverse operations are performed at aNodeB (decoding using a TC and encoding using a convolutional code suchas, for example, a TBCC).

While the invention has been shown and described with reference tocertain exemplary embodiments thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the presentinvention as defined by the appended claims and their equivalents.

What is claimed is:
 1. A method for a user equipment (UE), the methodcomprising: receiving first physical downlink control channel (PDCCH)candidates based on a first fixed number of PDCCH candidates perrespective control channel element (CCE) aggregation levels for a firstset of CCE aggregation levels, if a configuration related to a number ofPDCCH candidate per CCE aggregation level is not received by a higherlayer signaling; receiving, via a higher layer signaling, configurationinformation related to a second number of PDCCH candidates perrespective CCE aggregation levels in a second set of CCE aggregationlevels; and receiving second PDCCH candidates based on the second numberof PDCCH candidates per respective CCE aggregation levels in the secondset of CCE aggregation levels, after receiving the configurationinformation.